1. Interactions of Quasiparticles
Electrons, holes
Phonons
Photons
Defects
Rayleigh Scattering
(Section 5.3)
Rayleigh
Scattering
Dipole,
quadrupole
Interaction
(Section 5.2)
Plasticity
theory
Nonlinear
Optics
(Chap. 7)
Anharmonic
(Section 5.4)
Coulomb
scattering,
spin-spin
interaction
(Section 5.5)
Deformation potential,
Piezoelectric, Frölich
Scattering (Section 5.1)
Acousto-
optics
Elastic
scattering
Adapted from Snoke’s Solid State Physics

2. Defects in Solids
Mechanical and electrical properties of solids depend strongly on amount of defects
Surface/interface reconstruction
polystyrene spheres for self-assembled photonic crystals with intentional low-dimensional defects for defect-mode pass-band in stop-band of photonic bandgap

3. Interactions with Defects - Types of Defects
Vacancy
Ideal Crystal
Interstial
Substitutional
When might a line defect be favorable? When growing a material on another.

4. These are Point Defects
Consist of only one or a few atoms, does not necessarily involve foreign atoms
Vacancies: missing atoms, modeled by considering the energy required to break the bonds between an atom inside the crystal and its nearest neighbors
Frenkel defects: atom displaced from regular site to interstitial site
Vacancy + displaced atom = Frenkel pair

5. Dislocations is a line defect Two-dimensional defect
Dislocation is a common one
Results from local elastic stress
Described by Burgers vector
Constructed via closed loop around dislocation core
Edge dislocation: Burgers vector perpendicular to dislocation line
Screw dislocation: Burgers vector parallel to dislocation line 4 3 3
Start at M and count a 3x4 box around 4
Screw dislocation

6. Planar Defects in Solids
One case is a twin boundary (plane)
Essentially a reflection of atom positions across the twinning plane.
Stacking faults
For FCC metals an error in ABCABC packing sequence
Ex: ABCABABC
Adapted from Fig. 4.9, Callister 7e.

7. Defects in Metallic Crystals
Most metals crystallize in bcc, fcc or hcp structures
Changing pressure or temp. can interchange these forms for a metal
Soft and malleable metals usually have fcc structure (copper)
Harder and more brittle metals usually have the hcp structure (zinc)
Atoms can slide past each other and then realign into crystal form
Dislocations (imperfections in lattice) make it easier to bend
Impurities (imperfections in atom type) allow slippage of layers
Work Hardening means hammer until impurities are together
Heat: can soften by dispersing impurities or harden if control cooling
Mention shape memory alloys